Initial commit
Create dog_years.rb

Program to calculate the user's age in dog years
Update README.md
Create leapyear.rb

Program for calculating whether a given year is also a leap year
Create shopping_list.rb

Basic shopping list program.

TODO: practice loops per comments
Add string interpolation
Create gradebook.rb
Update string interpolation and method

Add string interpolation and remove unnecessary string cast method
Add remaining leap year logic